The present invention generally relates to a magnetic tape recording and/or reproducing apparatus such as, for example, a video tape recorder (VTR) or digital audio tape recorder (DAT) being capable of information recording and/or reproducing on and from a reeled length of magnetic tape. More particularly, the present invention relates to a protective enclosure for a magnetic recording and/or reproducing head assembly used in the magnetic tape recording and/or reproducing apparatus.
As is well known to those skilled in the art, and as shown in FIGS. 8 and 9 of the accompanying drawings which illustrate a video tape recorder in schematic top plan view and front elevational view, respectively, the conventional video tape recorder makes use of a magnetic recording and/or reproducing head assembly (hereinafter, simply referred to as "magnetic head assembly") which comprises a cylindrical drum assembly 1. The cylindrical drum assembly 1 comprises a stationary drum 103 rigidly mounted on a base plate 2, and a rotary drum 102 mounted atop the stationary drum 103 in coaxial relationship with said stationary drum 103 and carrying at least one magnetic recording and/or reproducing head 101 for rotation together therewith at a position adjacent the stationary drum 103, said rotary drum 102 being supported by and drivingly coupled with a drive shaft of an electric drive motor 3 that is carried by the stationary drum 103.
A length of magnetic tape 4 drawn out from a standardized tape cassette 6 loaded in a cassette chamber in the apparatus extends from a supply reel (not shown) within the tape cassette 6 to a take-up reel (not shown) also within the tape cassette 6, having been deflected by a leading guide post 5A so as to contact a portion of the cylindrical drum assembly 1. The tape 4 is then deflected again by a trailing guide post 5B and finally passed between a capstan 7 and a pinch roller 8. The capstan 7 is drivingly coupled with a separate drive motor or the same drive motor 3 through a reduction gear unit, and therefore, during the rotation of the capstan 7 in one direction, the length of magnetic tape 4 can be pulled from the supply reel onto the take-up reel while sandwiched between it and the pinch roller 8.
In practice, the leading and trailing guide posts 5A and 5B are supported for movement between retracted and operative positions and are normally held at the retracted position when and so long as the tape cassette 6 is not inserted into the cassette chamber. However, when the tape cassette is inserted into the cassette chamber and subsequently assumes a loaded position within the cassette chamber, the leading and trailing guide posts 5A and 5B in the retracted position protrude into a recess, defined at the front side of the tape cassette, and, as they move towards the operative position, pull a length of magnetic tape 4 towards the cylindrical drum assembly 1. With the leading and trailing guide posts 5A and 5B brought to the operative position as shown in FIG. 8, a portion of the magnetic tape 4 between the leading and trailing guide posts 5A and 5B is held in contact with that portion of the outer peripheral surface of the cylindrical drum assembly 1 and extends at a predetermined angle relative to the plane in which the magnetic recording and/or reproducing head 101 revolves together with the rotation of the rotary drum 102. This is well known as a helical scan system.
As a matter of design well known to those skilled in the art, during the actual information recording or reproduction with the head 101 scanning helically the length of magnetic tape 4 being moved from the supply reel onto the take-up reel, the rotary drum 102 carrying the head 101 is driven by the motor 3 at a high velocity relative to the speed of travel of the length of magnetic tape 4.
According to the prior art video tape recorder of the construction as hereinabove described, the cylindrical drum assembly 1 is left bared, that is, unprotected from dust and foreign matter within the cabinet of the magnetic tape recording and/or reproducing apparatus. Therefore, when the magnetic tape recording and/or reproducing apparatus is placed in the environment full of dust and foreign matter, for example, placed or installed in an automobile, dust and foreign matter are readily accessible into the cabinet of the apparatus, adhering to the outer peripheral surface of the cylindrical drum assembly 1. Once this happens, a detrimental problem occurs not only to the apparatus as a whole, but also to the magnetic tape. More specifically, if the cylindrical drum assembly is contaminated with the dust and the foreign matter, both of the length of magnetic tape 4 and the magnetic recording and/or reproducing head 101 are susceptible to abrasive wear which ultimately results in the failure of the both to exhibit their designed performance.
Moreover, where the prior art magnetic tape recording and/or reproducing apparatus of the type described hereinabove is placed or installed in the environment where a change in ambient temperature is pronounced, for example, during the winter season while the apparatus is positioned adjacent an air-conditioner grille inside an automobile, hot air emerging from the air-conditioner grille enters the cabinet of the apparatus and, as a result of the contact of the hot air with the peripheral surface of the cylindrical drum assembly which is still cool, the frosting takes place in the peripheral surface of the cylindrical drum assembly. Once the peripheral surface of the cylindrical drum assembly is frosted, that portion of the magnetic tape which has been turned around a portion of the outer peripheral surface of the cylindrical drum assembly sticks more or less to the outer peripheral surface of the cylindrical drum assembly with the result that proper movement of the magnetic tape is hampered to such an extent as to result in the entanglement of the magnetic tape inside the cabinet.